Circuit diagram based on bipolar junction transistor (BJT) voltage divider

When working with a bipolar junction transistor (BJT) voltage divider circuit, it's important to understand how the design affects power efficiency. The basic voltage divider shown in Figure 2 lacks a push-pull output stage, which can lead to significant power loss when no load is connected. To address this issue, we can implement a more efficient voltage divider using BJT transistors. This type of circuit is particularly useful when high output voltage, high current, or high power is required, and when precise voltage regulation isn't critical. In later examples, we'll explore a few practical applications that demonstrate the flexibility of these circuits. They offer simple control over the output voltage and push-pull configuration, similar to how transistor-based audio amplifiers operate as DC amplifiers. Figure 3 illustrates two basic voltage dividers constructed around two transistors. Transistors T1 and T2 act as buffers for the voltages generated by resistors R1 through R4 and diodes D1 and D2. These diodes help with temperature compensation, though they are optional. If used, D1 should be thermally connected to T1, and D2 to T2. If not used, the values of R2 and R3 should be adjusted accordingly. Resistors R5, R6, and R7 provide local feedback, helping to improve stability and protect the circuit. R5 is significantly larger than R6 and R7. Calculating component values in this setup follows a similar approach to that of an emitter follower circuit. In Figure 3b, three transistors are used along with a more advanced voltage regulation circuit featuring negative feedback. Resistor R1 and trimmer P1 provide the necessary feedback to stabilize the output voltage. The positive and negative output voltages (+V1 and -V2) are set using P1, R1, and R2. Diodes D1 and D2 again serve for temperature compensation. Resistors R4 and R5 add additional protection for the output transistors T2 and T3. If you need more precise control over the output voltage from the voltage divider, a differential amplifier built with transistors can be a great solution. Figure 4 shows a voltage divider based on five transistors (T1 to T5). T1 and T2 function as a differential amplifier, while T3 acts as an amplifier and driver for the output transistors T4 and T5. Resistor R6 provides negative feedback to stabilize the output voltage. R7 and C2 are not essential, but C1 is necessary for frequency compensation. The output voltages +V1 and -V2 are controlled by R1, R2, and P1. Diodes D1, D2, and D3 are used for biasing and temperature compensation of the output transistors. The trimmer P2 adjusts the quiescent current of the output transistors, typically ranging from 1mA to 10mA depending on the load. Resistors R4 and R5 offer local feedback and some level of protection for T4 and T5.